Surgical gowns, drapes and the like protect surgically prepared areas of the skin from contamination and also protect surgeons and nurses against contamination through contact with unprepared or contaminated areas of patient's skin. In addition, surgical gowns and drapes should present a sterile barrier to protect patients from contamination through contact with the surgeon.
Liquid repellency of the gown or drape is recognized as an important property in assuring that the gown or drape protects and acts as a barrier to the passage of bacteria or viruses carried in liquids. Body liquids and other liquids can permeate through the surgical gown or drape lacking liquid repellency properties. Thus, bacteria and viruses, such as the human immunodeficiency virus and hepatitis B virus, which may be present on the surface of the gown or drape can be transported through the gown to the patient or the operating room personnel.
In addition to being liquid repellent and a bacteria and viral barrier, hospital gowns and drapes desirably present a non-glare outer surface, are nonlinting, possess antistatic characteristics, and, not least importantly, are comfortable to wear.
It has been widely recognized that garments must be "breathable" to be comfortable. While it is not necessary, although preferable, that air pass through the garment for it to be comfortable, it is essential that water vapor from perspiration be transmitted from inside to outside so that a natural evaporative cooling effect can be achieved. If a continuous film of hydrophilic material is exposed to air containing a high concentration of water vapor on one side of the film, and to air containing a lower concentration of water vapor on the other side, the side of the film exposed to the higher water vapor concentration will absorb water molecules which diffuse through the film and are desorbed or evaporated on the side exposed to the lower water vapor concentration. Thus, in a continuous film of hydrophilic material, water vapor is effectively transported through the film on a molecule by molecule basis. This property is known as moisture vapor transmission. Generally, in microporous films water vapor is also transported by the diffusion of water vapor in the air which is able to permeate the membrane.
One type of commonly used protective clothing is made from nonwoven substrate calendared at high temperature and pressure. While having reasonable properties for protection, garments constructed of this material are known to be very uncomfortable due to their inherent low moisture vapor transmission and low air permeability characteristics, i.e., their low breathability. Various attempts have been made to improve breathability of this nonwoven material. These efforts, however, frequently result in a more open structure of the nonwoven material and thus also simultaneously lower its protection value. Coatings on polyolefin nonwovens have been employed to afford greater barrier protection to the `open` base structure of the nonwoven. However, the already inherently low moisture transmission and air permeability characteristics of the nonwoven material are even further reduced, simultaneously reducing the comfort of garments made by use of this technology.
Protective clothing in hospital operating rooms has been made of spun-laced nonwovens of polyester and wood pulp fibers, heavily treated with a water-repellent. Here, again, a compromise in properties must be reached. Greater comfort sacrifices maximum microorganism barrier protection and greater barrier protection lowers comfort. For instance, where hospital operating room gown products require superior protection from microorganisms, a dense, nonporous polyethylene film is usually laminated to the nonwoven. But, while achieving good barrier characteristics, moisture vapor transmission is substantially eliminated.
As seen from the foregoing, protection properties and comfort properties are traded off with one another. The present invention allows for both desirably good barrier protection characteristics while simultaneously achieving excellent moisture vapor transmitting characteristics, i.e. providing both protection and comfort.
U.S. Pat. No. 4,961,985 (Henn et al.) describes a coated product for use as a fabric for protective clothing. The product is made of a substrate and a coating comprised of a microporous scaffold material having a high void volume and open, interconnecting void microstructure, at least partially filled with a layer of a selected polyurethane. The product has viral barrier properties.
U.S. Pat. No. 5,017,292 (DiLeo et al.) describes a particular asymmetric composite membrane structure having skin possessing ultrafiltration separation properties, a porous substrate and a porous intermediate zone that is particularly useful for selectively isolating virus from a protein-containing solution.
Japanese Laid-Open (Kokai) Patent Application S.60-142860 (Kawase et al.) describes a method of removing viruses in water or a water solution by filtering through a porous polyolefin membrane having micropores with an average diameter of 0.05-0.30 mm, a pore rate of 30-90 (v/v)%, a thickness of 5-100 mm and air filtration velocity of 5-30.times.10.sup.4 l/m.sup.2 hr 0.5 atm at a between-membrane pressure difference of less than 2 kg/cm.sup.2.
Japanese Laid-Open (Kokai) Patent Application H. 1-305001 (Mitsutani) describes a method of preserving bulbs using a material which allows oxygen to pass through but prevents viruses from reaching the bulbs. The material is a film described as a porous, hydrophilic polyolefin, polyvinyl alcohol, cellulose acetate, regenerated cellulose, polypropylene, polyethylene, polyethylene copolymer, cellulose mixed ester resin and fluoride resin. The material may also be a solution that can be coated onto the bulb. This material should be water soluble, allow oxygen to pass through, but stop viruses. Examples of this material are cellulose acetate phthalate, methyl methacrylate methacrylic acid, polymer synthetic products, cellulose, and natural products.
Japanese Laid-Open (Kokai) Patent Application H2-212527 (Matsumoto) describes a method for making a porous filtration membrane by exposing a film to high energy particles, chemically etching the film to make uniform pore diameters, and graft polymerizing a hydrophilic monomer such as acrylic acid onto the porous film. The polymer for the film is selected from polyethylene, polypropylene, ethylene-alpha-olefin copolymer such as ethylene-propylene copolymer and polyvinylidene fluoride. The porous membrane described in this application can be used in the water system for separation of bacteria and viruses.
Japanese Laid-Open (Kokai) Patent Application S.64-22305 (Shiro) describes porous polypropylene fibers and the pathogenic agent filtering apparatus using these fibers. The apparatus can remove pathogenic agents (bacteria and viruses) contained in the serum from the blood of germ carriers. The hollow fiber is formed by special drawing and stretching conditions. The hollow fiber is characterized in that the pore shape is extremely uniform and the pore diameter distribution is narrow. The pore diameter is on the average of 50-250 nanometers.
U.S. Pat. No. 4,194,041 (Gore et al.) is representative of a number of patents which describe coatings or laminates purported to provide waterproof articles which do not leak when touched and are breathable. This patent describes a layered article for use in waterproof garments or tents comprising at least two layers: an interior, continuous hydrophilic layer that readily allows water vapor to diffuse therethrough, prevents the transport of surface active agents and contaminating substances such as those found in perspiration, and is substantially resistant to pressure induced flow of liquid water, and a hydrophobic layer that permits the transmission of water vapor and provides thermal insulating properties even when exposed to rain. The hydrophobic layer is preferably waterproof microporous tetrafluoroethylene (PTFE) or polypropylene, which permits the passage of moisture vapor through the pores thereof. The hydrophilic layer transfers moisture vapor therethrough whereupon it passes through the porous hydrophobic layer. Various means of joining the layers are suggested including the application of hydraulic pressure to force the hydrophilic polymer to penetrate into the surface void spaces of the hydrophobic layer.
U.S. Pat. No. 4,443,511 (Worden et al.) discloses a layered waterproof, breathable and stretchable article for use in, for example, material for protective articles. Also disclosed is a waterproof and breathable elastomeric polytetrafluoroethylene layered article bonded to a stretch fabric. The water proof and breathable elastomeric polytetrafluoroethylene layered article bonded to a stretch fabric is described as durable and possessing a moisture vapor transmission rate exceeding 1000 gms/m.sup.2 day.
U.S. Pat. No. 4,613,544 (Burleigh) describes a waterproof, moisture vapor permeable unitary sheet material comprising a microporous polymeric matrix having pores comprising continuous passages extending through its thickness and opening into the opposite surfaces thereof, the passages being sufficiently filled with a moisture vapor permeable, water impermeable, hydrophilic material to prevent the passage of water and other liquids through the unitary sheet material while readily permitting moisture vapor transmission therethrough rendering the sheet material breathable. The unitary sheet is made by causing a liquid composition comprising the hydrophilic material or precursor thereof to flow into the pores of the matrix, then causing the conversion thereof to solid hydrophilic material.
While these materials alleviate some of the problems known to the art, many require lamination to protect the water repellent, moisture vapor permeable material they use in their constructions while others require void filling which can lower the moisture vapor transmission rate of the material and decrease its ability to heat seal. Joining of multiple pieces of these materials in a three dimensional garment presents additional problems in that most of these materials are not readily joined together by any means other than sewing which creates needle holes that must be subsequently sealed with seaming tapes or alternative filling techniques to provide a totally waterproof garment. Also, due to the dense nature of the hydrophilic layer, many of these materials are minimally permeable to air.
U.S. Pat. No. 5,025,052 (Crater et al.) describes fluorochemical oxazolidinone compositions and their use for oil and water repellency in films, fibers, and non-woven webs.
U.S. Pat. No. 4,539,256 (Shipman) discloses a microporous sheet material formed by liquid-solid phase separation of a crystallizable thermoplastic polymer with a compound which is miscible with the thermoplastic polymer at the melting temperature of the polymer but phase separates on cooling at or below the crystallization temperature of the polymer.
U.S. Pat. No. 4,726,989 (Mrozinski) discloses a microporous material similar to that of Shipman but which also incorporates a nucleating agent.
U.S. Pat. No. 4,867,881 (Kinzer) discloses an oriented microporous film formed by liquid--liquid phase separation of a crystalline thermoplastic polymer and a compatible liquid.
The present invention relates to a method of preventing transmission of viral pathogens between a source of viral pathogens and a target of said viral pathogens comprising positioning between said source and said target a microporous membrane material comprising (1) a thermoplastic polymer or polytetrafluoroethylene and (2) a water- and oil-repellent fluorochemical compound which provides said membrane with oleophobic, hydrophobic and viral barrier properties. The fluorochemical compound can be introduced as a melt additive during the membrane preparation or as a topical treatment after the membrane is made. The membrane material is moisture vapor, air permeable and sweat contamination resistant. The membrane material is also heat sealable when made using a thermoplastic polymer.
In a preferred embodiment, the membrane comprises (1) a crystallized olefin polymer, and, disposed within the pores a processing compound which is miscible with the olefin polymer at the melting point of the polymer but phase separates on cooling to or below the crystallization temperature of the polymer and (2) a fluorochemical oxazolidinone compound, a fluorochemical aminoalcohol compound, an amorphous fluoropolymer, a fluoroacrylate polymer, a fluorochemical piperazine, a fluorochemical acrylic ester or a blend thereof.
In another preferred embodiment of the invention, the microporous membrane comprises (1) a polyolefin resin or a blend of polyolefin resins (2) finely divided inorganic filler material having a melting point above the polyolefin degradation temperature(s) and (3) a fluorochemical compound which provides the membrane with viral barrier properties, the membrane being oriented in at least one direction. Generally, the fluorochemical compound is a water- and oil-repellent fluorochemical compound. Preferred fluorochemical compounds include fluorochemical oxazolidinones, fluorochemical aminoalcohols, amorphous fluoropolymers, fluoroacrylate polymers, fluorochemical piperazines, fluorochemical stearates and blends thereof.
The present invention further provides a microporous membrane material and articles such as surgical gowns, drapes, masks, gloves, sterile wraps, wound dressings and waste disposal bags for containment of virally contaminated materials, comprising (1) a thermoplastic polymer or polytetrafluoroethylene and (2) a water- and oil-repellent fluorochemical compound which provides said membrane with oleophobic, hydrophobic and viral barrier properties. The articles may be disposable or reusable.
The microporous membrane materials useful in the present invention retain their viral barrier, liquid repellency and moisture vapor and air permeability properties for extended periods even in garment and surgical drape applications which expose the membrane materials to perspiration residues which are known to contaminate and ultimately destroy repellency properties of conventional liquid repellent, moisture vapor permeable materials. Surprisingly, the materials useful in the invention prepared by incorporating the fluorochemical compound as a melt additive retain this contamination resistance to perspiration despite the presence of the processing compound, an oleophilic material. Further, the microporous membrane materials useful in the invention repel mineral oil even when they contain mineral oil. The microporous membrane materials useful in the present invention also possess excellent hand and drape properties.